CALDER, an ancient district of Midlothian, Scotland. It is divided into the parishes of Mid-Calder (pop. 1931, 2,793) and West Calder (pop. 6,817), East Calder belonging to the parish of Kirknewton. The locality owes some of its commercial im portance to the mineral oil industry, which, however, has now declined. Coal is mined, sandstone and limestone are worked, and paper is made. Mid-Calder, a town on the Almond, has an ancient church, and John Spottiswood (1510-1585), the Scottish reformer, was for many years minister. The town of West Calder (PoP. 3,949), within the parish of that name, is situated on Breich Water, an affluent of the Almond, 151 m. S.W. of Edinburgh by the L.M.S.R., and is the chief centre of the district. At Addie well, about II m. S.W., the manufacture of ammonia, naphtha, paraffin oil and candles is carried on; the village dates from 1866, and had in 1921 a population of 3,141. Oil is also refined at Pumpherston. The district contains several tumuli, old ruined castles and a Roman camp which is in a state of comparatively good preservation.